The present invention relates to a method forming an electrical element or antenna. More specifically, the present invention relates to a method for making an electrical element or antenna by printing a conductive ink over a pattern-printed coating.
Conductive inks are used for printing electrical elements, including antennae. In particular, conductive inks have been used to print antennae for radio frequency identification (RFID) tags. RFID tags are used to track inventory, confirm the validity of goods, and for other product tracking and identification purposes.
Printed ink electrical components can be less expensive to produce than their formed, stamped, or laser ablated counterparts. In addition, printed ink electrical components can be presented in an aesthetically pleasing manner. This is particularly important when considering the use of printed ink antennae for use in tracking retail goods, since the common retail tracking system uses a large unsightly tag, as opposed to the more decorative tag afforded by using a printed ink antenna.
One current problem with printed ink electrical elements is that the current printing technologies (using a screen-printing process) result in ink bleeding, which causes the conductive path in the element to short circuit. This problem is exaggerated for RFID antennae because a long uninterrupted conductive path in an RFID antenna provides a more powerful antenna; ink bleeding becomes more probable with this longer path. Thus there is a need for making long uninterrupted paths of printed conductive ink. The present invention provides a process for printing such paths of conductive ink, and also discloses using this process in antennae and RFID applications.
The present invention provides a printing process in which a conductive ink is printed over a coating having an additive that lowers surface tension. The coating with the surface tension lowering additive is pattern printed on a substrate in a predetermined pattern, and a conductive ink is then applied over the coating. Due to the difference in surface tension between the coating and the substrate, the ink flows away from the coating, forming the shape for a conductive element.
The conductive element may be an antennae or an RFID antennae.